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libc: minimal: add console system calls

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The stdout console implementations for minimal libc call directly into
the various console drivers (depending on what specifc hooks are
registered) causing faults when invoked from user mode. This happens,
for example, when using printf() which eventually ends up calling
fputc().

The proper solution is to ensure privileges have been elevated before
the _stdout_hook is called. This was already done for printk().

puts() and fputs() have now been re-defined in terms of the
fputc() and fwrite() functions, which are now system calls.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
This commit is contained in:
Andrew Boie 2018-03-26 16:57:25 -07:00 • committed by Anas Nashif
commit bc94cc1832
2 changed files with 70 additions and 16 deletions
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28
include/misc/libc-hooks.h Normal file
View file

@ -0,0 +1,28 @@
/*
* Copyright (c) 2018, Intel Corporation.
*
* SPDX-License-Identifier: Apache-2.0
*/
#ifndef ZEPHYR_LIBC_HOOKS_H
#define ZEPHYR_LIBC_HOOKS_H
#include <toolchain.h>
#include <stdio.h>
#include <stddef.h>
/*
* Private header for specifying accessory functions to the C library internals
* that need to call into the kernel as system calls
*/
/* Minimal libc */
__syscall int _zephyr_fputc(int c, FILE *stream);
__syscall size_t _zephyr_fwrite(const void *_MLIBC_RESTRICT ptr, size_t size,
size_t nitems, FILE *_MLIBC_RESTRICT stream);
#include <syscalls/libc-hooks.h>
#endif /* ZEPHYR_LIBC_HOOKS_H */

58
lib/libc/minimal/source/stdout/stdout_console.c
View file

@ -7,6 +7,9 @@
*/
#include <stdio.h>
#include <misc/libc-hooks.h>
#include <syscall_handler.h>
#include <string.h>
static int _stdout_hook_default(int c)
{
@ -22,29 +25,35 @@ void __stdout_hook_install(int (*hook)(int))
_stdout_hook = hook;
}
int fputc(int c, FILE *stream)
int _impl__zephyr_fputc(int c, FILE *stream)
{
return (stdout == stream) ? _stdout_hook(c) : EOF;
}
int fputs(const char *_MLIBC_RESTRICT string, FILE *_MLIBC_RESTRICT stream)
#ifdef CONFIG_USERSPACE
Z_SYSCALL_HANDLER(_zephyr_fputc, c, stream)
{
if (stream != stdout) {
return EOF;
}
return _impl__zephyr_fputc(c, (FILE *)stream);
}
#endif
while (*string != '\0') {
if (_stdout_hook((int)*string) == EOF) {
return EOF;
}
string++;
}
return 0;
int fputc(int c, FILE *stream)
{
return _zephyr_fputc(c, stream);
}
size_t fwrite(const void *_MLIBC_RESTRICT ptr, size_t size, size_t nitems,
FILE *_MLIBC_RESTRICT stream)
int fputs(const char *_MLIBC_RESTRICT string, FILE *_MLIBC_RESTRICT stream)
{
int len = strlen(string);
int ret;
ret = fwrite(string, len, 1, stream);
return len == ret ? 0 : EOF;
}
size_t _impl__zephyr_fwrite(const void *_MLIBC_RESTRICT ptr, size_t size,
size_t nitems, FILE *_MLIBC_RESTRICT stream)
{
size_t i;
size_t j;
@ -71,11 +80,28 @@ done:
return (nitems - i);
}
#ifdef CONFIG_USERSPACE
Z_SYSCALL_HANDLER(_zephyr_fwrite, ptr, size, nitems, stream)
{
Z_OOPS(Z_SYSCALL_MEMORY_ARRAY_READ(ptr, nitems, size));
return _impl__zephyr_fwrite((const void *_MLIBC_RESTRICT)ptr, size,
nitems, (FILE *_MLIBC_RESTRICT)stream);
}
#endif
size_t fwrite(const void *_MLIBC_RESTRICT ptr, size_t size, size_t nitems,
FILE *_MLIBC_RESTRICT stream)
{
return _zephyr_fwrite(ptr, size, nitems, stream);
}
int puts(const char *string)
{
if (fputs(string, stdout) == EOF) {
return EOF;
}
return (_stdout_hook((int) '\n') == EOF) ? EOF : 0;
return fputc('\n', stdout) == EOF ? EOF : 0;
}